Femtosecond pulsed laser ablation of 3C-SiC thin film on silicon

A femtosecond pulsed Ti:sapphire laser (pulse width = 120 fs, wavelength = 800 nm, repetition rate = 1 kHz) was employed to perform laser ablation of 1 mum-thick silicon carbide (3C-SiC) films grown on silicon substrates. The threshold fluence and ablation rate, useful for the micromachining of the 3C-SiC films, were experimentally determined. The material removal mechanisms vary depending on the applied energy fluence. At high laser fluence, a thermally dominated process such as melting, boiling and vaporizing of single-crystal SiC occurs. At low laser fluence, the ablation is a defect-activation process via incubation, defect accumulation, formation of nanoparticles and final vaporization of boundaries. The defect-activation process reduces the ablation threshold fluence and enhances lateral and vertical precision as compared to the thermally dominated mechanism. Helium, as an assistant gas, plays a major role in improving the processing quality and ablation rate of SiC thin films due to its inertness and high first ionization energy.